KVM: lib: use jump label to handle resource release in irq_bypass_register_consumer()

Use out_err jump label to handle resource release. It's a
good practice to release resource in one place and help
eliminate some duplicated code.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>